In the existing telephone network, customers are assigned telephone numbers based upon where their telephones are geographically located or fixed. For example, each telephone number may contain numbers representing (1) a three-digit numbering plan area code (NPA code) which uniquely identifies a defined geographic area at which the customer's telephone is located, (2) a three-digit end office code (NXX) identifying a central office exchange that handles calls within that geographic area, and then (3) a four-digit line number uniquely representing the customer within the central office exchange.
The existing telephone network is conventionally made up of a series of connected telephone switches, each operated by a local telephone service provider and designated to handle calls for particular customers within a service area. Many calls require switches operated by different local telephone service providers to interact with each other to establish necessary links. In those cases, the switch at the calling party attempts to locate the switch at the called party by accessing a database of network addresses indexed according to NPA code and NXX. After receiving the network address for the called party's switch, the calling party's switch establishes a link between the switches and transmits a request for the called party's switch to complete the call to the called party.
This configuration is not adaptive to customer needs, however. For example, the network does not conveniently support "local number portability," meaning the ability of a customer to retain his telephone number when switching local telephone service providers. This often requires customers to change telephone numbers when they move from one service area to another, creating an inconvenience. This configuration also does not allow a customer to select different service providers to concurrently provide different services or features to that customer.
Increases in customer mobility and demand for portability have prompted a proposal to modify the existing telephone network to support local number portability. Such modifications may involve maintaining in a database detailed records containing information indicating, for example, which services are provided to a customer and which service providers are selected to provide those services. Such detailed records, however, must be accurately and frequently updated so that switches can rely upon those records to provide effective service to their customers. Thus, there is a need to provide a mechanism for maintaining such records within the existing telephone network. In systems providing for local number portability when there are record changes, including those caused by a number plan area split.